First steps

Requirements

• Have at least a basic knowledge of EMF (Eclipse Modeling Framework).
• Have installed ALE.

Objectives

• Discover the structure of an ALE project through a built-in example.
• Launch your first ALE program.

Get the HelloWorld example

ALE provides an Hello world! project template:

1. File > New > Example...
2. EcoreTools ALE Examples > Hello world!
3. Select helloworld
4. Finish

After a few seconds a new project called helloworld should be created in your workspace. This project defines a simple HelloWorld EClass able to print “Hello world!”. The content of the project is presented below.

What we have inside

The interesting files of the helloworld project are inside the folder model:

By opening HelloWorld.aird you will see the HelloWorld EClass and its properties:

As you can see, all the members of HelloWorld are displayed in a bold font. That indicates that they are defined inside HelloWorld.ale.

Note: if the members are not shown make sure that the Behavior layer is activated.

HelloWorld.ale contains the following code:

behavior HelloWorld;

open class HelloWorld {             // 1

    String msg := 'Hello world!';   // 2

    override EString greeting() {   // 3
        result := self.msg;         // 4
    }

    @main                           // 5
    def void entryPoint() {
        self.greeting().log();      // 6
    }
}

• ① Indicates that modify the HelloWorld EClass.
• ② Declare a new attribute of type String. Defining msg within HelloWorls.ale makes it a runtime data. In other words, it does not exist in the metamodel and will be created by the ALE interpreter during the execution.
• ③ Specify the semantics of the greeting operation.
• ④ Return the value of the msg attribute (there is no return statement in ALE).
• ⑤ Indicate that the entryPoint operation is the entry point of the execution and should be called by the ALE interpreter.
• ⑥ Print "Hello world!".

Tip: see the Reference page for a detailed overview of ALE’s syntax.

Run!

The execution can be launched through the contextual menu:

1. Right-click on HelloWorld.dsl
2. Select Run As > ALE launch, a dialog should open asking you to select the model to interpret
3. Make sure HelloWorld.xmi is selected then click on OK.
4. Witness the result on the console:

Run helloworld.dsl
------------
Hello world!

Conclusion

Now that we covered the basics of ALE you’re ready to go further with the MiniFsm tutorial.